function sim = linearKernel(x1, x2)
    %LINEARKERNEL returns a linear kernel between x1 and x2
    %   sim = linearKernel(x1, x2) returns a linear kernel between x1 and x2
    %   and returns the value in sim

    % Ensure that x1 and x2 are column vectors
    x1 = x1(:); x2 = x2(:);

    % Compute the kernel
    sim = x1' * x2; % dot product

end
